Existing prosthetic joint bearings are often configured to maintain congruent contact with the hones or prosthetics forming the joint throughout the range of joint movement.
In order to maintain congruent contact, it is often necessary for the bearings to take a non-anatomical shape. This is because previous anatomically shaped prosthetic bearings have not been suitable for maintaining congruent contact throughout the range of joint movement, as they are not able to mimic the natural flexibility of cartilage white remaining rigid enough to support the joint adequately.
An aim of the present invention is to allow the use of anatomical components and a congruent bearing in a low wear bearing combination. The bearing may achieve fully congruent contact throughout the full range of flexion, extension and rotation of a joint. In the case of a bearing for use in a knee prosthesis, the bearing is suitable for use with an anatomical (poly-radial, poly-centric) femoral component or a spherical femoral component.
The bearing maintains the low wear and extended range of movement associated with a fully congruent bearing design but allows the use of anatomical femoral and tibial surfaces. In addition, due to the material properties of the bearing, this design offers: shock absorbance, increased longevity, increased intraoperative flexibility, unique patient fit and placement, improved kinematics, ability to be used on young active patients and ease of revision. Further, it may be possible to use thinner components to allow increased bone conservation.
Also, it is an aim of the invention to allow the use of prosthetics wherein more of the natural joint is retained. For example, if the bearing is used in a prosthetic knee replacement (unicompartmental or otherwise), it may be possible to retain the natural condyles on the femur and/or tibia for use with the bearing. Only condyles which actually require replacement would have to be replaced. An improved bearing which allows more of the natural tissue to be retained has obvious benefits for the patient. Further, as the tearing is typically more flexible than existing bearings, it can be inserted or replaced using a smaller incision, which is less traumatic for a patient.